A cluster of virtual machines across physical ESXi hosts (also known as a cluster across boxes or CAB) protects against software failures and hardware failures on the physical ESXi hosts by placing the cluster nodes on separate ESXi hosts. This configuration requires shared storage for the clustered disk resources.

The following figure shows a cluster-across-boxes setup.

  • Two virtual machines on two different ESXi hosts run WSFC.
  • The virtual machines share a private network connection for the private heartbeat and a public network connection.
  • Each virtual machine is connected to shared storage.
Note: In a cluster of virtual machines across physical hosts, shared disks can be physical mode or vVol with vSphere 6.7 or later. You can use VMFS VMDKs with vSphere 7.0 or later. If you are using RDMs or vVol as shared disks, they can be on Fibre Channel (FC) SAN, FCoE or iSCSI. If you are using VMFS VMDKs as shared disks, they must be on FC SAN only. A clustered disk must have a homogenous set of disks. This means that if the configuration is done with FC SAN, then all of the cluster disks should be FC SAN only. Mixed mode is not supported.
Figure 1. Virtual Machines Clustered Across Hosts

Clustering virtual machines across hosts
Note: Windows Server 2008 SP2 and above systems support up to five nodes (virtual machines). For supported guest operating systems see Other Clustering Requirements and Recommendations.
Note: Private and Public network interconnect can share a single virtual NIC in a VM.

You can expand the cluster-across-boxes model and place multiple virtual machines on multiple ESXi hosts. For example, you can consolidate three clusters of two physical machines each to two ESXi hosts with four virtual machines each.